Fast Li+ Transport Polyurethane-Based Single-Ion Conducting Polymer Electrolyte with Sulfonamide Side chains in the Hard Segment for Lithium Metal Batteries

Molecular Mechanisms Driving the Performance of Single-Ion Conducting Polymer Electrolytes in Lithium-Based Batteries

Single-ion conducting polymer electrolytes (SICPEs) hold great potential for the next-generation batteries due to their high safety, fast charging capability, and high energy density. However, their practical application is hindered by the low ionic conductivity (IC). The addition of plasticizers has been shown to effectively enhance IC, although the underlying molecular mechanisms remain unclear. In this study, we employed atomistic molecular dynamics simulations to examine the impact of ethylene carbonate (EC) on lithium-ionic conductivity in a modified polyethylene terephthalate (mPET)-based SICPE. Our simulations reproduced experimental IC values and revealed a similar IC trend with varying EC concentrations, including a notable transition at 50 wt % EC. This enhancement in IC appears to be associated with increased EC diffusion and the preferential coordination of the lithium ions with the oxygen atoms in EC. Analysis of the local oxygen coordination environment around lithium ions further explains the IC transition observed at 50 wt % EC. These findings provide insights into the molecular mechanisms by which EC enhances IC in mPET-based SICPEs, primarily through changes in the local oxygen environment surrounding lithium ions. This study contributes to the design of improved SICPEs with plasticizers, supporting advancements in lithium-ion battery technology.

Realization of Enhanced Interfacial Lithium-Ion Transfer in Composite Polymer Electrolytes via Grafting Oligo-PEG Molecular Brushes on Silica-Coated Nanofibers for All-Solid-State Lithium Metal Batteries

Polyether-based polymer electrolytes are attractive but still challenging for high-energy-density solid-state lithium metal batteries due to their limited Li-ion conductivity at room temperature. Herein, an oligomeric polyethylene glycol methyl ether methacrylate (PEGMEM)-modified silica-coated polyimide fibrous scaffold (PINF@PEGMEM-SiO2) was introduced in polyethylene glycol dimethyl ether (PEGDME) to enhance the Li-ion transportation at room temperature. PINF@PEGMEM-SiO2 was developed to build a continuous and interconnected interface for continuous Li-ion transportation in bulk. The carbonyl groups (C═O) of PEGMEM on SiO2 can promote the dissociation of lithium salts and enhance the migration of free Li ions at the interface. The same -C-C-O- unit contained in both PEGMEM and PEGDME ensures the compatibility of PEGMEM at the interface and PEGDME in the bulk. The prepared PEGDME-based polymer electrolyte exhibits a high ionic conductivity of 1.14 × 10-4 S cm-1 at 25 °C and an improved Li-ion transference number of 0.41. Furthermore, LiFePO4/Li and LiNi0.8Co0.1Mn0.1O2/Li cells with excellent cyclability and rate capability at ambient temperature are obtained.

A Healable Quasi-Solid Polymer Electrolyte with Balanced Toughness and Ionic Conductivity

Solid polymer electrolytes (SPEs) have garnered extensive attention as potential alternatives to traditional liquid electrolytes, primarily due to their prowess in curbing lithium dendrite formation and preventing electrolyte leaks. The quest for SPEs that are both mechanically robust and exhibit superior ionic conductivity has been vigorous. However, achieving a harmonious balance between these two attributes remains a significant challenge. In this study, we introduce a novel quasi-solid electrolyte, ingeniously crafted from a poly(urethane-urea) network, enriched with lithium salts and plasticizers. This innovative composition not only boasts remarkable toughness but also ensures commendable ionic conductivity. Our post-gelation method yields gel polymer electrolytes that undergo rigorous evaluation, leading to an optimized version that stands out with its exceptional room-temperature ionic conductivity (2.94×10-4 S cm-1) and outstanding toughness (11.9 MJ m-3). Moreover, it demonstrates a broad electrochemical window (4.73 V), remarkable stability across a 600-hour cycle test, a high capacity retention exceeding 80 % after 100 cycles at 0.2 C, and a noteworthy self-healing capability. This quasi-solid polymer electrolyte emerges as a promising contender to replace current liquid electrolyte solutions.